Aircraft typically include pitot-static systems which are used to determine the longitudinal air speed and the altitude of the aircraft. The pitot system includes one or more pitot tubes which project out of the airframe, into the air stream, and allow the impact pressure of the atmosphere to enter the tube(s). Sensors sense a pressure differential to create an air speed indicative output. The pressure differential can be between the impact air pressure from the pitot tube and static air pressure from a static port. The air speed indicative output is provided, typically by an air data computer, to an air speed indicator in the cockpit.
The static system typically includes two or more of the static pressure ports which sense the atmospheric pressure outside of the aircraft, ideally without being influenced by pressure variances caused by movement of the aircraft. The standard atmospheric pressure sensed by the static ports is used to generate altitude indicative signals which are provided, typically by the air data computer, to an altimeter in the cockpit of the aircraft. Frequently, in newer aircraft, the static ports are integral to the pitot tubes.
The pitot tube(s) and static ports of a pitot-static system can sometimes develop blockages which seriously affect the accuracy of the sensed pressures, and therefore seriously affect the accuracy of the determined air speed and altitude. The pitot tubes and static ports can be blocked with foreign materials such as insects, birds, and ice, for example. In other instances, the static ports or pitot tube openings have been taped shut during maintenance of the aircraft, and accidentally left blocked. Erroneous air speed and altitude determinations made as a result of these blockages can create a dangerous operating situation for the aircraft.